Journal of Atmospheric Chemistry最新文献

To assess the efficacy of the “Implementation Details of Air Pollution Prevention and Control Action Plan”, the chemical composition of PM_2.5 and other pollutants was determined during the winters of 2013–2014 and 2016–2017 at two urban sites in Xiangtan City, Hunan. The concentrations of PM_2.5, SO₂, and NO₂ decreased from 146.0 to 94.5?μg/m³, 75.9 to 33.5?μg/m³, and 80.6 to 55.8?μg/m³, respectively, from winter 2013–2014 to winter 2016–2017. The concentrations of almost all the major chemical components of PM_2.5 decreased as well, particularly secondary inorganic aerosols (SIAs). These results indicate that the implementation of the air quality control plan was very effective in improving air quality. Analysis of the data also suggests that SIA formation is likely responsible for high winter PM_2.5 pollution and that high relative humidity levels and low wind speed can promote the formation of SIA. A 72-h back trajectory analysis shows that both regional transport and the accumulation of local pollutants under stagnant meteorological conditions promote the occurrence of episodes of high wintertime pollution levels.

Particle morphology and elemental compositions are among the crucial parameters of aerosols required for accurate understanding of the climatic effect of aerosols in the earth-atmosphere system; yet their vertical distributions and region specific properties are poorly characterised due to sparse in-situ measurements. This is the first study to classify and quantify the vertical distributions of the morphological characteristics and elemental composition of aerosols based on single particle as well as bulk chemical analysis over seven geographically diverse regions of northern and central parts of India during spring (April–May, 2013), carried out as a part of Regional Aerosol Warming Experiment (RAWEX). Significant regional distinctiveness in shapes (non-sphericity), sizes and elemental compositions of the airborne particles were conspicuous, having dominance of highly irregular granular aggregates over the north Indian sites. The non-spherical coarse mode particles dominated the lower free tropospheric regions (> 2?km) of the Indo-Gangetic Plains (IGP). These particles could be responsible for enhanced spring time aerosol absorption in the elevated region of the atmosphere. Elemental compositions of the single particle analysis indicate that the free tropospheric layer over the IGP and central India is enriched with Na and Ca compounds mixed with Fe or Al (soil particles), indicating long range transport of crustal aerosols. This finding is very well supported by the bulk particle analysis indicating abundance of Ca²⁺ in the free troposphere with low contribution of ssNa⁺. Particles with irregular rough surfaces having dominance of SiO₂ were observed over all the study sites. The percentage share of spherical (either smooth or rough) particles to the total morphological characteristics of the particles was found to be highly subdued (< 10%). The present study thus critically assesses the relevant knowledge pertaining to the morphological features of aerosols over the IGP during spring for the accurate estimation of aerosol radiative properties. More such efforts are required in future to study the connections and dependencies between morphological and radiative properties of aerosols in different seasons.

This paper presents the trends of gaseous nitric acid, nitrogen dioxide, sulfur dioxide, ammonia and nitrate, ammonium, sulfate ions in atmospheric air, and nitrate, ammonium and sulfate ions in wet deposition over 2008–2018 in Armenia. Atmospheric nitrogen and sulfur concentrations were monitored by data obtained from filter pack samplers and glass sinter filters at background monitoring station of Armenia (Amberd), which is designated as EMEP (European Monitoring and Evaluation Programme) station. Laboratory analyses were performed by ion chromatography system and UV spectrophotometer. MAKESENS programme was used for detecting and estimating trends in the time series of annual average values of atmospheric concentrations. Long term trends of atmospheric concentrations of nitrogen and sulfur compounds at the Amberd air quality monitoring station were calculated and discussed for the investigated decade. The trends significance levels for all parameters are calculated. It is identified that there are no significant trends for all explored paramenters, except reduced sulfur in aerosols. Possible emission and deposition changes of nitrogen and sulfur compounds in Armenia were explored in order to identify possible transboundary air pollution and its main sources. Deposition data was estimated by EMEP MSC-W model calculations. Investigation of transboundary fluxes of nitrogen and sulfur compounds displays main receptor areas and contributors. Analysis of seasonality in atmospheric pollutants shows strong seasonal behaviour of the measured parameters in wet deposition - higher concentrations during summertime compared with the wintertime. Atmospheric concentrations of nitrate and ammonium ions are lower during summertime compared with the wintertime, while ammonia has low concentrations during wintertime. Atmospheric nitric acid, sulfate ion, sulfur dioxide and nitrogen dioxide revel no significant seasonality.

Humic-like substances (HULIS), the most ubiquitous class of water-soluble organic compounds in the atmosphere could enhance the generation of reactive oxygen species (ROS), and play a significant role in impacting aerosol chemistry and health effects. In this study, twenty-three PM_2.5 samples were collected in the atmosphere of suburban Shanghai from November 29 to December 17, 2015, and March 17 to April 30, 2016, during haze and non-haze days. The mean concentrations of HULIS in spring both in haze and non-haze days (2.34?±?0.70 μg/m³ and 1.94?±?0.88 μg/m³) were relatively higher than in that of winter (1.93?±?0.95 μg/m³ and 1.31?±?0.28 μg/m³). The ammonium, sulfate, and nitrate are the dominant ionic species in both winter and spring during haze days in suburban Shanghai. Correlation results revealed that HULIS formation was highly associated with the biomass burning (K) and secondary aerosols formation (SIA: NH₄⁺, SO₄^2?, NO₃^?) and also well-correlated with F^? and ca.²⁺ ions, crustal elements (Al and Fe) and anthropogenic pollution metals (As, Se, Rb, Sr, and Pb), suggesting that HULIS-C formation might be from biomass burning and secondary aerosol processes and also mixed formation (marine, crustal and industrial emissions) sources. From the coinciding results of the clustering analysis and weighted-CWT model, the principal potential source regions were the short transports from the Yangtze River Delta (YRD) regions, local regions, marine areas (the Bohai Sea, the Yellow Sea, the East China Sea) and also the long-range transports from northwestern in those seasons.

The chemical composition of particulate matter impacts both human health and climate. In this study, the chemical characteristics of particulate matter was measured for four months (November 2016–February 2017) at Varanasi, which is located in the middle of the Indo-Gangetic Basin (IGB). The daily observed mean values of PM₁₀ and PM_2.5 are 134?±?48 and 213?±?80?μg/m³, respectively, which exceeds both national and international standards. The average value of PM_2.5/PM₁₀ ratio is 0.64?±?0.16 which indicates a relatively higher fraction of fine particles that are attributed to anthropogenic emission sources (biomass/post-harvest burning) as corroborated by MODIS fire counts and back trajectory analysis. Ion chromatographic measurements showed that SO₄^2?, Cl^?, K⁺, NO₃^?, Na⁺, Ca²⁺, Mg²⁺ are the major ionic species present in the aerosol. Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM–EDX) analysis shows the prevalence of carbon-rich particles at Varanasi which is likely due to biomass burning and other anthropogenic sources.

Clouds, fogs, and rain can serve as useful integrators of both atmospheric aerosols and soluble trace gases. To better understand the chemical characteristics of sea fog and rain in the North and South Pacific Ocean, fog and rain were measured aboard the R/V ARAON in 2012 and 2014, respectively, as part of the Ship-borne Pole-to-Pole Observations (SHIPPO) project. The mean sea fog pH (3.59) was lower than the mean rain pH (4.54), reflecting greater inputs of non-sea-salt (nss)-SO₄^2?. For the collected rain, nss-Ca²⁺ and nss-Mg²⁺ from mineral dust particles were the major contributors to acidity neutralization. NO₃^? concentrations, which are derived from scavenging of gaseous nitric acid and aerosol nitrate, were higher than NH₄⁺ concentrations, indicating that terrestrial and/or local anthropogenic NO₃^? sources outweighed contributions from anthropogenic or biological oceanic NH₃/NH₄⁺ sources. The ratio of Cl^?/Na⁺ in the sea fog was slightly lower than that in the sea water due to HCl volatilization from scavenged sea-salt particles. The ratio of NH₄⁺/ nss-Ca²⁺ was lower in the rain than in the sea fog, revealing the influence of mineral dust particles at altitudes above the sea fog layer. The average sea fog water TOC concentration, 13.2 ppmC, was much higher than the measured TOC concentrations in marine fogs and clouds in other remote environments, likely due to continental influence; the TN and TOC concentrations in the fog water were much higher than those in the rain. The sea fog and rain chemical properties measured during research cruises like these enhance our understanding of wet deposition and cloud condensation nuclei sources and processes in the Pacific Ocean.

The concentrations of suspended particulate matter PM10 in two-month winter period, i.e. December–January in years 2009–2015, were analyzed in relation to the values of wind speed in that time. It was possible to analyze results of air pollution measurements performed in the measuring station from the perspective of their higher levels in winter seasons (so-called smog episodes). Results from 3 stations of the Regional Inspectorate for Environmental Protection in Poznań (WIO? Poznań) served for better presentation of smog episodes in the region (black smog) and aimed at verification of correctness of the measurements of pollution immission in the monitoring station in Piotrkowice which is situated in vicinity of large combustion plant. The analysis confirmed that with low speeds of wind higher values of particulate matter PM10 were observed. The results of the analysis also show the displacement of pollutants according to the current wind direction or their local persistence for a longer time over one area.

The properties of the atmospheric aerosols depend on the source region and on the modifications that occur during their transport in the air. We have studied physical and chemical properties of aerosols along with their sink mechanism over two locations in southwest India, an urban site (Pune) and well-established climate observatory at Sinhagad (SINH), which represents rural and high altitude site. The ground-based measurements of aerosols, together with their radiative properties in this study have provided means to understand the observed variability and the impact on the aerosol radiative properties effectively over this region. The annual mean elemental carbon concentration (3.4 μg m^??3) at Pune was observed about three times higher compared to SINH (1.3 μg m^??3), indicating strong emissions of carbon-rich aerosols at the urban location. Aerosol optical properties were derived using the OPAC model which were used to compute the Aerosol radiative forcing (ARF) over both stations calculated using SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model shows pronounced seasonal variations due to changes in aerosol optical depth and single scattering albedo at both locations. The year-round ARF was 4–5 times higher over Pune (31.4?±?3.5 Wm^??2) compared to SINH (7.2?±?1.1 Wm^??2). The atmospheric heating rate due to aerosols shows a similar pattern as ARF for these locations. The heating was higher in the wintertime, ~?0.9–1.6 K day^??1 at Pune, and ~?0.3–0.6 K day^??1 at SINH. The estimated scavenging ratio was found high for NO₃^? and Ca.²⁺. The wet deposition fluxes of Cl^?, SO₄^2?, Na⁺, Mg²⁺ were observed higher for SINH as compared to Pune, due to the high amount of rain received at SINH.

The major ions in precipitation can reflect the conditions of the atmosphere, while stable isotopic characteristics provide information on the moisture source. In order to understand the local hydro-chemical features and regional geochemical cycle, it is essential to assess the chemical composition of precipitation and the associated sources. Therefore, a total of 57 precipitation samples (2016 to 2017) for major ions and 178 samples (2013 to 2017) for stable isotopes were collected from the Wengguo station and analyzed to explore the major ionic deposition and stable isotopic characteristics in the northern slopes of the Himalayas. The average pH and electrical conductivity were 6.82?±?0.45 and 15.36?±?11.67 μS cm^?1, respectively. Ca²⁺ followed by K⁺ and Mg²⁺ played a crucial role in neutralizing the precipitation acidity. The major ionic sources in the region were terrigenous (Ca²⁺, HCO₃^?, and Mg²⁺) and sea salt (Na⁺, Cl^?, and Mg²⁺), as well as anthropogenic emissions (SO₄^2? and NO₃^?) and biomass burning (K⁺). The total deposition flux of the major ions was higher in 2016 than in 2017 and was influenced by the higher precipitation. The average values of δ¹⁸O and δD in precipitation were???15.22?±?5.17 ‰ and???116.01?±?41.31 ‰, respectively. The precipitation stable isotopes were not significantly correlated to the local air temperature but the precipitation amount. Moreover, the variation in stable isotopes, local meteoric water line, and d-excess indicated the existence of continental and monsoon moisture transport systems. The transport of chemicals over the high elevation region from polluted cities in South Asia via moisture originating in the Bay of Bengal and the Arabian Sea was determined based on the source identification, clusters of air mass backward trajectory analysis, and the National Center for Environmental Prediction Final dataset. Thus, the ionic concentrations and stable isotopic characteristics of the precipitation from this study provided a valuable dataset to assess the atmospheric environment in the northern slopes of the Himalayas at Southern Tibetan Plateau.